LONCHOPHYLLA DEKEYSERI´S PERSISTENCE AND RABIES MANAGEMENT

Ludmilla Moura de Souza Aguiar1, Daniel Brito2 , Ricardo B. Machado3 (Laboratório de Ecologia de Vertebrados, Embrapa Cerrados – CPAC, Rodovia BR 020, km 18, Caixa Postal 08223, 73310- 970, Planaltina, Distrito Federal, Brazil. Conservation International 2, Conservação Internacional do Brasil3)

Keywords: agroecosystem, Cerrado, conservation, rotundus, management, population viability analysis, rabies control, Vortex

Introduction

Bats compose more than 50% of the fauna in the Cerrado (Aguiar & Zortéa 2008), and play key services like acting as pollinators of Cerrado plants, seed dispersers trough the degraded areas of the region, and predators of agriculture plagues (Aguiar & Antonini 2008). However, since their identification as a vector for rabies, farmers are always complaining about staunted by the fear of livestock losses. Aguiar et al (2006) observed that for each L. dekeyseri captured in the Distrito Federal region there were 4.55 D. rotundus. Populations are in private land where close entrances of caves or warfarin are used to kill bats, regardless of their species. Analyses of factors influencing population viability are crucial for populations management of threatened species (Morris & Doak 2002). Our objective is to evaluate if the current practices to manage vampire populations (D. rotundus), within a region where cattle ranching is economically important, could pose a threat to the persistence of Lonchophylla dekeyseri, a threatened endemic nectarivorous bat of the Cerrado.

Material and Methods Lonchophylla dekeyseri occurs in 36 localities that are structured into six populations. It is known to share roosts with D. rotundus (Aguiar et al. 2006a). Demographic data that were input to Vortex are based on six populations that can hold up to around 120 individuals with an estimated total population of only 720 bats in the wild. For the baseline scenario we used the demographic data considering no inbreeding depression and no rabies management. We used median of 3.14 lethal equivalents per individual (Ralls et al. 1988) and also decided to model scenarios of rabies management with different severities to the population: low mortality (where 25% of the population

is exterminated), medium mortality (where 50% of the population is exterminated) and high mortality (where 75% of the population is exterminated), with a probability of occurrence of 10% per year for each population. We also modeled scenarios with both threats (inbreeding depression and rabies management) affecting the populations synergistically. Populations are considered viable if they have ≥ 95% chance of persistence (Shaffer 1981) and retain ≥ 90% of their original heterozygosis (Foose 1993).

Results and Discussion Our results suggest that even though the populations and the metapopulation are small, they show low probabilities of extinction under the baseline scenario (Table 1). But, when modeling scenarios with both inbreeding depression and rabies management scenarios acting synergistically, we observe some worrying results. The scenario modeling inbreeding depression and low mortality rabies management results in declines in growth rate and population size (Table 1). However, the scenarios modeling inbreeding depression coupled with medium and high mortality rabies management resulted in marked declines in the survival probability, heterozigosity, growth rate and population size both for populations and the metapopulation (Table 1). Our data show that inbreeding depression alone does not affect the dynamics of the populations or the metapopulation. But suggest that rabies management has a more serious impact in L. dekeyseri populations, and inbreeding depression has a secondary, but also noticeable, deleterious effect. Dimitrov et al. (2007) have shown trough modeling that the persistence of the rabies virus in bat population is not significantly affected by the particular initial distributions, but it is strongly related to the removal rate. A relatively low removal rate guarantees an endemic state of the infection, characterized by a small portion of infected individuals and a large portion of exposed and immune bats. However, enormous quantities of bats were and are killed in government- supported programmes in Brazil. These actions are regarded by farmers and local and national authorities as necessary control measures against the ‘plague’ of bats and the danger of rabies transmission (Mayen 2003).

Table 1: Growth rates (r) and mean time to extinction (TE), for L. dekeyseri populations (a) and metapopulation (b) under different scenarios (for scenario descriptions see text) in the Cerrado.

Scenarios Population Metapopulation r TE R TE Baseline 0.1055 - 0.1069 - Inbreeding depression 0.0853 - 0.0866 - Rabies 25 0.0764 - 0.0810 - Rabies 50 0.0339 63.02 0.0527 - Rabies 75 -0.0246 42.73 0.0011 7590 Inbreeding depression + rabies 25 0.0549 65.00 0.0597 - Inbreeding depression + rabies 50 0.0038 67.90 0.0220 93.71 Inbreeding depression + rabies 75 -0.0466 40.25 -0.0323 70.44

Conclusion The current ineffective bat-extermination policy to reduce D. rotundus populations may threaten other bat species, like L. dekeyseri, which are extremely important for ecological processes and ecosystem services in the Cerrado (Coelho & Marinho Filho 2004, Aguiar et al. 2006). Such bad management practices, coupled with inbreeding depression, may prove to be the demise of L. dekeyseri. Habitat loss and fragmentation is a severe threat and is responsible for the first blow to the species persistence, making it more vulnerable to inbreeding depression and stochastic events (Brito & Fernandez 2000). Inappropriate rabies management to deal with public health issues may represent the coup de grace to L. dekeyseri if no changes in the current management practices to deal with rabies are taken.

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